Canadian patent No 359,235 issued in 1936 to Milton KALISCHER discloses an air conditioning apparatus including a blower unit with separate heating and cooling coils for heating or cooling air drawn through the unit. More particularly, the apparatus comprises a first set of heating tubes and a second set of cooling tubes, and a common set of fins providing extended heating surfaces for the heating tubes, when heating fluid is circulated therethrough, and extended cooling surfaces for the cooling tubes, when cooling fluid is circulated therethrough. Such an apparatus is very inefficient in the use of available space.
U.S. Pat. No. 4,134,448 issued 16 Jan. 1979 to the corporation Raytheon Co. shows a single heat exchanger for air, with valve means to selectively provide hot or cold fluid to the heat exchanger to heat or cool the air. The furnace and the water heater are linked by water pipe lines 28, 30, including a water pump 40, so that the air conditioning system be driven by the furnace or the water heater depending on the outdoor climatic load sustained, whereby more efficient operations of the furnace and of the water heater are achieved. The compressor and condensor unit 18 is located exteriorly of the dwelling.
Canadian patent No 1,189,703 issued 2 Jul. 1985 to the Hussmann corp. also discloses an apparatus which can both heat and cool recirculated room air in an alternate fashion. Again, the condensor 44 is located exteriorly of the dwelling to be heated or cooled. Moreover, this system is mainly directed to be beneficial in commercial and industrial installations, such as food markets, convenience stores, restaurants, warehouses and manufacturing or processing facilities having primary refrigeration systems to 0provide multiple refrigeration needs.
Canadian patent No 1,129,198 issued 10 Aug. 1982 to Intertherm inc. discloses a compact electric furnace combined with an air conditioning system. An externally located module must still be envisioned.
U.S. Pat. No. 3,308,805 issued in 1967 to Hans Stockli discloses a combined heating and air conditioning apparatus. Again, a refrigerant gaz, namely, FREON (a trademark) is supplied to the evaporators through a pipe from an externally located condensor; the evaporated refrigerant is returned to the compressor of the refrigerating plant through another pipe.
U.S. Pat. No. 4,125,151 issued Nov. 14, 1978 to the Raytheon Company discloses a compact heating and cooling system, where all the system except the air ducts are located outside of the dwelling to be heated.backslash.cooled.
U.S. Pat. No. 4,825,847 issued 2 May 1989 to the present applicant discloses a furnace unit including a water tank. A heating element is immersed in the water tank to heat the water, whereby a pump recirculates the water from the tank to a radiator. A water vapor by-pass tube interconnects the water tank to the air outlet duct, so as to humidify the air warmed by the radiator. No add-on air conditioning device is envisioned. Known air cooling systems where the compressor and air cooled condenser are located outside the house, require a thermostat to shut off the compressor operation when the outside temperature drops below about 50.degree. F. to prevent compressor damage due to cold weather. Thus the air cooling system cannot be used in winter in cold climate regions.